Okay, this is relevant for two reasons: 1) it deals with a government agency, and 2) it brings to light a great use of a mashup. It's irrelevant and fun because 3) it deals with my geeky interest in Star Wars.
I love that I live in a country where they wrap USPS mailboxes like R2D2.
Which brings me to another reason to love mashups: locations of R2D2 mailboxes across the nation. (There's one in Fort Worth--and in Abilene! I'll have to make a special trip to see it while we're there this weekend.)